Ultralow threshold field emission from ZnO nanorod arrays grown on ZnO film at low temperature

ZnO nanorod arrays have been synthesized on silicon substrate covered with ZnO film by thermal evaporation of zinc particles at a low temperature of 550 °C. Their field emission has been investigated: the turn-on electric field (at the current density of 1 µA cm⁻²) is about 3.8 V µm⁻¹, and the threshold electric field (at the current density of 1 mA cm⁻²) is 6.3 V µm⁻¹ at the working distance of 100 µm. In comparison, the turn-on and threshold electric fields of the not well-aligned ZnO nanorod arrays and ZnO film are 9.8, 15.8 V µm⁻¹ and 13.7, 26.0 V µm⁻¹ at 100 µm, respectively. These behaviors indicate that such an ultralow threshold field emission is attributed to the aligned structure, the good electric contact with the conducting substrate where they grow, and weaker field-screening effect. Our results demonstrate that well-aligned nanorod arrays with excellent field-emission performance grown at such a low temperature can provide the possibility of application in glass-sealed flat panel displays.